U.S. patent application number 13/644831 was filed with the patent office on 2013-04-18 for wood-type golf club.
This patent application is currently assigned to DUNLOP SPORTS CO. LTD.. The applicant listed for this patent is Dunlop Sports Co. Ltd.. Invention is credited to Hiroshi HASEGAWA, Takashi NAKAMURA, Takashi NAKANO.
Application Number | 20130095944 13/644831 |
Document ID | / |
Family ID | 48054561 |
Filed Date | 2013-04-18 |
United States Patent
Application |
20130095944 |
Kind Code |
A1 |
NAKAMURA; Takashi ; et
al. |
April 18, 2013 |
WOOD-TYPE GOLF CLUB
Abstract
Provided is a golf club having a head disposed at a front end of
a shaft and a grip disposed at a back end of the shaft. A club
weight is not larger than 290 g. A product of a ratio (head
weight/club weight) of a head weight to the club weight, and a
ratio (L.sub.G/L.sub.S) of a distance L.sub.G from the front end of
the shaft to a center of gravity of the shaft to a full length
L.sub.S of the shaft, is not smaller than 0.365.
Inventors: |
NAKAMURA; Takashi; (Kobe,
JP) ; HASEGAWA; Hiroshi; (Kobe, JP) ; NAKANO;
Takashi; (Kobe, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Dunlop Sports Co. Ltd.; |
Kobe |
|
JP |
|
|
Assignee: |
DUNLOP SPORTS CO. LTD.
Kobe
JP
|
Family ID: |
48054561 |
Appl. No.: |
13/644831 |
Filed: |
October 4, 2012 |
Current U.S.
Class: |
473/292 |
Current CPC
Class: |
A63B 53/00 20130101;
A63B 60/42 20151001; A63B 53/08 20130101; A63B 53/0466 20130101;
A63B 53/14 20130101; A63B 53/10 20130101; A63B 2209/023 20130101;
A63B 53/0408 20200801 |
Class at
Publication: |
473/292 |
International
Class: |
A63B 53/00 20060101
A63B053/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 12, 2011 |
JP |
2011-224700 |
Claims
1. A wood-type golf club having a head disposed at a front end of a
shaft and a grip disposed at a back end of the shaft, wherein a
club weight is not larger than 340 g, and a product of a ratio
(head weight/club weight) of a head weight to the club weight, and
a ratio (L.sub.G/L.sub.S) of a distance L.sub.G from the front end
of the shaft to a center of gravity of the shaft to a full length
L.sub.S of the shaft, is not smaller than 0.365.
2. The wood-type golf club according to claim 1, wherein the ratio
(head weight/club weight) of the head weight to the club weight is
not lower than 0.6 but not higher than 0.77.
3. The wood-type golf club according to claim 1, wherein the ratio
(L.sub.G/L.sub.S) of the distance L.sub.G from the front end of the
shaft to the center of gravity of the shaft to the full length
L.sub.S of the shaft is not lower than 0.5 but not higher than
0.67.
4. The wood-type golf club according to claim 1, wherein the
product is not smaller than 0.365 but not larger than 0.4.
5. The wood-type golf club according to claim 1, wherein a length
of the club is not smaller than 39 inches but not larger than 46
inches.
6. The wood-type golf club according to claim 1, wherein the club
weight is not smaller than 265 g but not larger than 340 g.
7. The wood-type golf club according to claim 1, wherein the ratio
of the head weight to the club weight is not lower than 0.64 but
not higher than 0.74.
8. The wood-type golf club according to claim 1, wherein a weight
of the grip is not smaller than 28 g but not larger than 50 g.
9. The wood-type golf club according to claim 1, wherein a weight
of the shaft is not smaller than 35 g but not larger than 70 g.
10. The wood-type golf club according to claim 1, wherein the
length of the shaft is not smaller than 990 mm but not larger than
1200 mm.
11. The wood-type golf club according to claim 1, wherein said
L.sub.G/L.sub.S is not lower than 0.53.
12. The wood-type golf club according to claim 1, wherein the
product of the (head weight/club weight) and the (L.sub.G/L.sub.S)
is not smaller than 0.368.
13. The wood-type golf club according to claim 1, wherein the
product of the (head weight/club weight) and the (L.sub.G/L.sub.S)
is not larger than 0.398.
14. The wood-type golf club according to claim 1, wherein a weight
of a butt partial layer of the shaft with respect to a weight of
the shaft is not smaller than 5 wt % but not larger than 50 wt
%.
15. The wood-type golf club according to claim 1, wherein when a
weight of a butt partial layer existing in a range from a butt end
of the shaft to a point separated from the butt end by 250 mm is
represented as Wa, and when a weight of the shaft in said range is
represented as Wb, Wa/Wb is not lower than 0.4 but not higher than
0.7.
16. The wood-type golf club according to claim 1, wherein a fiber
elastic modulus of a butt partial layer is not lower than 5
t/mm.sup.2 but not higher than 20 t/mm.sup.2.
17. The wood-type golf club according to claim 1, wherein a resin
content of a butt partial layer is not lower than 20 mass % but not
higher than 50 mass %.
18. The wood-type golf club according to claim 1, wherein a weight
of a butt straight layer with respect to a weight of the shaft is
not smaller than 5 mass % but not larger than 50 mass %.
19. The wood-type golf club according to claim 1, wherein a fiber
elastic modulus of a butt straight layer is not lower than 5
t/mm.sup.2 but not higher than 20 t/mm.sup.2.
20. The wood-type golf club according to claim 1, wherein a resin
content of a butt straight layer is not lower than 20 mass % but
not higher than 50 mass %.
Description
TECHNICAL FIELD
[0001] The present invention relates to a wood-type golf club.
BACKGROUND ART
[0002] For golfers, flight distance of a ball is one of the
important factors when selecting a golf club. Therefore, hitherto,
in order to extend the flight distance of the ball, various
improvements have been made with regard to shapes and materials of
elements forming a golf club.
[0003] For example, when the weight of a head is large, kinetic
energy provided to a ball when the ball is hit becomes large and
the speed of the ball can be increased, and, as a result, a large
flight distance can be obtained. Therefore, a technique for
increasing a head weight by increasing the proportion of the head
weight with respect to the total weight of a golf club has been
proposed (e.g., see Patent Literature 1).
CITATION LIST
Patent Literature
[0004] [PTL1] Japanese Laid-Open Patent Publication No.
2004-201911
SUMMARY OF INVENTION
Technical Problem
[0005] Although it is possible to increase kinetic energy of a head
by increasing the weight of the head, when the head weight is
simply increased, inertia moment at a grip end of a club becomes
large. Therefore, a head speed decreases due to swinging becoming
difficult, and thereby the kinetic energy of the head cannot be
effectively increased even with the increase in the head weight. As
a result, a large flight distance of a ball cannot be obtained.
[0006] The present invention is made in view of such a situation,
and an objective of the present invention is to provide a wood-type
golf club that is easy to swing and is capable of increasing head
speed.
Solution to Problem
[0007] (1) A wood-type golf club of the present invention is a
wood-type golf club having a head disposed at a front end of a
shaft and a grip disposed at a back end of the shaft, wherein
[0008] a club weight is not larger than 340 g, and
[0009] a product of a ratio (head weight/club weight) of a head
weight to the club weight, and a ratio (L.sub.G/L.sub.S) of a
distance L.sub.G from the front end of the shaft to a center of
gravity of the shaft to a full length L.sub.S of the shaft, is not
smaller than 0.365.
[0010] In the wood-type golf club of the present invention, a
product of the ratio (head weight/club weight) of the head weight
to the club weight, and the ratio (L.sub.G/L.sub.S) of the distance
L.sub.G from the front end of the shaft to the center of gravity of
the shaft to the full length L.sub.S of the shaft, is set to be not
smaller than 0.365. As a result, the center of gravity of the shaft
can be brought close to the hand side while increasing the
proportion of the head weight with respect to the club weight.
[0011] As done hitherto, when the head weight is merely increased
to increase the proportion of the head weight with respect to the
club weight, an inertia moment at the grip end of the club becomes
large and swinging becomes difficult. As a result, a head speed
cannot be increased, and it is not possible to effectively increase
kinetic energy given to a ball when the ball is hit.
[0012] On the other hand, by setting the above described product to
be not smaller than 0.365, the center of gravity of the shaft can
be brought close to the hand side while increasing the proportion
of the head weight with respect to the club weight. By bringing the
center of gravity of the shaft close to the hand side, the inertia
moment at the grip end of the club becomes small, and swinging
becomes easy. With this, the head speed can be increased while
having a large head weight, and the kinetic energy of the head can
be effectively increased. As a result, a large flight distance of
the ball can be obtained.
[0013] Furthermore, even when the proportion of the head weight
with respect to the club weight is small, by setting up the above
described range (0.365.ltoreq.product), the center of gravity of
the shaft can be brought largely close to the hand side, and the
inertia moment at the grip end of the club can be further reduced.
With this, the swinging becomes further easy, and the head speed
can be further increased. Therefore, in this case, since the head
speed can be largely increased instead of reducing the head weight,
a large flight distance can be obtained overall.
[0014] (2) In the wood-type golf club of (1), the ratio (head
weight/club weight) of the head weight to the club weight may be
not lower than 0.6 but not higher than 0.77.
[0015] (3) In the wood-type golf club of (1) or (2), the ratio
(L.sub.G/L.sub.S) of the distance L.sub.G from the front end of the
shaft to the center of gravity of the shaft to the full length
L.sub.S of the shaft may be not lower than 0.5 but not higher than
0.67.
[0016] (4) In the wood-type golf club of (1) or (2), the product
may be not smaller than 0.365 but not larger than 0.4.
[0017] (5) In the wood-type golf club of (1) or (2), the club
length may be not smaller than 39 inches but not larger than 46
inches.
Advantageous Effects of Invention
[0018] According to the wood-type golf club of the present
invention, swinging becomes easy and the head speed can be
increased.
BRIEF DESCRIPTION OF DRAWINGS
[0019] FIG. 1 is an illustrative diagram of one embodiment of a
wood-type golf club of the present invention;
[0020] FIG. 2 is an expansion plan of a shaft of the wood-type golf
club shown in FIG. 1;
[0021] FIG. 3 is a plan view of a first merged sheet in the shaft
shown in FIG. 2;
[0022] FIG. 4 is a plan view of a second merged sheet in the shaft
shown in FIG. 2;
[0023] FIG. 5 is an expansion plan of a prepreg sheet included in a
modification of the shaft of the present invention;
[0024] FIG. 6 is a plan view of a first merged sheet of the shaft
shown in FIG. 5; and
[0025] FIG. 7 is a plan view of a second merged sheet of the shaft
shown in FIG. 5.
DESCRIPTION OF EMBODIMENTS
[0026] In the following, embodiments of the wood-type golf club
(hereinafter, also referred simply as "golf club") of the present
invention will be described in detail with reference to the
accompanying drawings. It should be noted that, in the present
specification, a "wood-type golf club" refers to clubs including
drivers, fairway woods, and utility clubs, whose club weights are
not larger than 340 g.
[0027] FIG. 1 is an illustrative diagram showing the entirety of a
golf club 1 according to one embodiment of the present invention.
The golf club 1 of the present embodiment includes a wood-type golf
club head 2 having a predetermined loft angle, a shaft 3, and a
grip 4. The head 2 includes a hosel 6 having a shaft hole 5 to
which a tip end 3a located at the front end side of the shaft 3 is
inserted and fixed. A butt end 3b at the back end side of the shaft
3 is inserted and fixed in a grip hole 7 of the grip 4. The tip end
3a is located inside the head 2, and the butt end 3b is located
inside the grip 4. It should be noted that, in FIG. 1, a reference
character of "G" indicates the center of gravity of the shaft 3.
The center of gravity G is located on a shaft axis inside the shaft
3.
[0028] The present invention relates to a wood-type golf club
including drivers, fairway woods, and utility clubs, whose club
weights are not larger than 340 g; and, in particular, when the
flight distance of a hit ball is considered, the present invention
can be suitably applied to a wood-type golf club whose club weight
is from 265 to 340 g.
[0029] Furthermore, although the length of the golf club 1 itself
is not particularly limited in the present invention, ordinarily,
the length is from 39 to 46 inches. It should be noted that, in the
present specification, "club length" is a length measured based on
the description in "Appendix II--Design of Clubs" "1. Clubs" "1c.
Length" in the Rules of Golf determined by R&A (The Royal and
Ancient Golf Club of Saint Andrews).
[0030] [Head Configuration]
[0031] The head 2 in the present embodiment is a hollow head and
has a large inertia moment. For a club having the head 2 with a
large inertia moment, the head 2 is preferably hollow since the
advantageous effect of improving flight distance can be stably
obtained.
[0032] There is no particular limitation in the material of the
head 2 in the present invention, and, for example, titanium,
titanium alloys, CFRPs (carbon fiber reinforced plastics),
stainless steel, maraging steel, soft iron, and the like can be
used. Furthermore, instead of manufacturing the head 2 using a
single material, the head 2 may be manufactured by combining
multiple materials as appropriate. For example, a CFRP and a
titanium alloy can be combined together. From a standpoint of
lowering the center of gravity of the head 2, it is possible to
employ a head in which at least a portion of a crown is made from a
CFRP, and at least a portion of a sole is made from a titanium
alloy. In addition, from a standpoint of strength, the entirety of
a face is preferably made from a titanium alloy.
[0033] Furthermore, in the golf club 1 of the present invention,
although there is no particular limitation in the ratio (head
weight/club weight) itself of the head weight to the club weight,
the ratio is preferably set to be not lower than 0.6 but not higher
than 0.77. If this ratio is too low, the kinetic energy of the head
2 becomes small and obtaining a sufficient ball speed becomes
difficult. Therefore, the ratio is further preferably not lower
than 0.62, and particularly preferably not lower than 0.64. On the
other hand, if the ratio is too high, weight that takes into
consideration the strengths of the shaft and the grip cannot be
ensured, and the strengths of the shaft and the grip may
deteriorate. Therefore, the ratio is further preferably not higher
than 0.74, and particularly preferably not higher than 0.73.
[0034] [Grip Configuration]
[0035] In the present invention, there is no particular limitation
in the material and structure of the grip 4, and those commonly
used can be adopted as appropriate. For example, there can be used
one that is obtained by blending and kneading natural rubber, oil,
carbon black, sulfur, and zinc oxide, and molding and vulcanizing
the materials into a predetermined shape.
[0036] In the present invention, although the weight of the grip 4
itself is not particularly limited, it is preferably not smaller
than 28 g but not larger than 50 g. If the weight of the grip 4 is
too small, the strength of the grip 4 becomes low, and its
durability may deteriorate. Therefore, the weight of the grip 4 is
further preferably not smaller than 30 g, and particularly
preferably not smaller than 32 g. On the other hand, if the weight
of the grip 4 is too large, the golf club 1 becomes heavy and
difficult to swing. Therefore, the weight of the grip 4 is further
preferably not larger than 48 g, and particularly preferably not
larger than 46 g.
[0037] [Shaft Configuration]
[0038] The shaft 3 in the present embodiment is a carbon shaft, and
is manufactured through an ordinarily sheet winding process using a
prepreg sheet as a material. In more detail, the shaft 3 is a
tubular body formed from a laminated body of a fiber reinforced
resin layer, and has a hollow structure. The full length of the
shaft 3 is represented as L.sub.S, and the distance from the tip
end (front end) 3a of the shaft 3 to the center of gravity G of the
shaft 3 is represented as L.sub.G.
[0039] Although weight of the shaft 3 is not particularly limited
in the present invention, it is ordinarily within a range from 35
to 70 g. If the weight of the shaft 3 is too small, the strength of
the shaft 3 becomes low, and its durability may deteriorate.
Therefore, the weight of the shaft 3 is preferably not smaller than
38 g, and further preferably not smaller than 40 g. On the other
hand, if the weight of the shaft 3 is too large, the golf club 1
becomes heavy and difficult to swing. Therefore, the weight of the
shaft 3 is preferably not larger than 65 g, and further preferably
not larger than 62 g.
[0040] Further, although the length of the shaft 3 itself is not
particularly limited in the present invention, it is ordinarily
from 990 to 1200 mm.
[0041] Furthermore, in the present embodiment, when the distance
from the front end of the shaft 3 to the center of gravity G of the
shaft is represented as L.sub.G and when the full length of the
shaft 3 is represented as L.sub.S, although there is no particular
limitation in the ratio (L.sub.G/L.sub.S) itself, the ratio
preferably satisfies 0.5.ltoreq.L.sub.G/L.sub.S.ltoreq.0.67.
[0042] If L.sub.G/L.sub.S is lower than 0.5, since the center of
gravity of the club becomes close to the head side, swinging
becomes difficult and sufficient head speed may not be obtained.
Therefore, L.sub.G/L.sub.S is preferably not lower than 0.52, and
further preferably not lower than 0.53.
[0043] On the other hand, if L.sub.G/L.sub.S is higher than 0.67,
the weight on the hand side of the shaft becomes large and the
weight on the front end side of the shaft becomes small when the
weight of the shaft is unchanged. As a result, the strength on the
front end side of the shaft becomes weak, and its durability
becomes deteriorated. Therefore, L.sub.G/L.sub.S is preferably not
higher than 0.66, and further preferably not higher than 0.65.
[0044] In the present invention, the product of the ratio (head
weight/club weight) of the head weight to the club weight and
L.sub.G/L.sub.S is set in a predetermined range, more specifically,
the product is set to be not smaller than 0.365. From a standpoint
of increasing the head weight and the head speed and obtaining a
large flight distance of a ball, the product is preferably not
smaller than 0.368, and further preferably not smaller than 0.37.
On the other hand, with regard to the upper limit of the product,
the product is preferably not larger than 0.4. In this case, load
on the shaft can be prevented from becoming excessively large, and
durability of the shaft can be prevented from deteriorating. From
this standpoint, the product is further preferably not larger than
0.398, and particularly preferably not larger than 0.395.
[0045] The shaft 3 can be manufactured by curing a prepreg sheet,
and fibers in this prepreg sheet are orientated substantially in
one direction. A prepreg whose fibers are orientated substantially
in one direction is also referred to as a UD (Uni-Direction)
prepreg. It should be noted that, in the present invention,
prepregs other than a UD prepreg can also be used, and, for
example, a prepreg sheet in which fibers included in the sheet are
knitted can also be used.
[0046] The prepreg sheet includes a matrix resin formed from a
thermosetting resin and the like, and a fiber such as a carbon
fiber. As described above, although the shaft 3 can be manufactured
through a sheet winding process, the matrix resin is in a
semi-cured state in a prepreg form. The shaft 3 is obtained by
winding and curing the prepreg. The curing of the prepreg is
conducted by applying heat, and steps for manufacturing the shaft 3
include a heating step. The matrix resin in the prepreg sheet is
cured in this heating step.
[0047] The matrix resin of the prepreg sheet is also not
particularly limited in the present invention, and, for example,
thermoplastic resins and thermosetting resins such as epoxy resins
can be used. From a standpoint of enhancing the strength of the
shaft, an epoxy resin is preferably used.
[0048] As the prepreg, a commercially available product can be used
as appropriate, and the following Table 1-1 and Table 1-2 show
examples of prepregs that can be used as the shaft of the golf club
of the present invention.
TABLE-US-00001 TABLE 1-1 Example of Usable Prepreg Fiber Resin
Prepreg Sheet Content Content Sheet Stock Thickness (Mass (Mass
Manufacturer Name Number (mm) %) %) Toray Industries, Inc. 3255S-10
0.082 76 24 Toray Industries, Inc. 3255S-12 0.103 76 24 Toray
Industries, Inc. 3255S-15 0.123 76 24 Toray Industries, Inc. 805S-3
0.034 60 40 Toray Industries, Inc. 2255S-10 0.082 76 24 Toray
Industries, Inc. 2255S-12 0.102 76 24 Toray Industries, Inc.
2255S-15 0.123 76 24 Toray Industries, Inc. 2256S-10 0.077 80 20
Toray Industries, Inc. 2256S-12 0.103 80 20 Toray Industries, Inc.
9255S-8 0.061 76 24 Nippon Graphite E1026A-09N 0.100 63 37 Fiber
Corp. Nippon Graphite E1026A-14N 0.150 63 37 Fiber Corp. Mitsubishi
Rayon TR350C-100S 0.083 75 25 Co., Ltd. Mitsubishi Rayon
TR350C-125S 0.104 75 25 Co., Ltd. Mitsubishi Rayon TR350C-150S
0.124 75 25 Co., Ltd. Mitsubishi Rayon TR350C-175S 0.146 75 25 Co.,
Ltd. Mitsubishi Rayon MR350C-075S 0.063 75 25 Co., Ltd. Mitsubishi
Rayon MR350C-100S 0.085 75 25 Co., Ltd. Mitsubishi Rayon
MR350C-125S 0.105 75 25 Co., Ltd. Mitsubishi Rayon MR350E-100S
0.093 70 30 Co., Ltd. Mitsubishi Rayon HRX350C-075S 0.057 75 25
Co., Ltd. Mitsubishi Rayon HRX350C-110S 0.082 75 25 Co., Ltd.
TABLE-US-00002 TABLE 1-2 Example of Usable Prepreg Carbon Fiber
Physical Property Value Carbon Tensile Prepreg Fiber Elastic
Tensile Sheet Stock Stock Modulus* Strength* Manufacturer Name
Number Number (t/mm.sup.2) (kgf/mm.sup.2) Toray Industries, Inc.
3255S-10 T700S 23.5 500 Toray Industries, Inc. 3255S-12 T700S 23.5
500 Toray Industries, Inc. 3255S-15 T700S 23.5 500 Toray
Industries, Inc. 805S-3 M30S 30 560 Toray Industries, Inc. 2255S-10
T800S 30 600 Toray Industries, Inc. 2255S-12 T800S 30 600 Toray
Industries, Inc. 2255S-15 T800S 30 600 Toray Industries, Inc.
2256S-10 T800S 30 600 Toray Industries, Inc. 2256S-12 T800S 30 600
Toray Industries, Inc. 9255S-8 M40S 40 470 Nippon Graphite
E1026A-09N XN-10 10 190 Fiber Corp. Nippon Graphite E1026A-14N
XN-10 10 190 Fiber Corp. Mitsubishi Rayon TR350C-100S TR50S 24 500
Co., Ltd. Mitsubishi Rayon TR350C-125S TR50S 24 500 Co., Ltd.
Mitsubishi Rayon TR350C-150S TR50S 24 500 Co., Ltd. Mitsubishi
Rayon TR350C-175S TR50S 24 500 Co., Ltd. Mitsubishi Rayon
MR350C-075S MR40 30 450 Co., Ltd. Mitsubishi Rayon MR350C-100S MR40
30 450 Co., Ltd. Mitsubishi Rayon MR350C-125S MR40 30 450 Co., Ltd.
Mitsubishi Rayon MR350E-100S MR40 30 450 Co., Ltd. Mitsubishi Rayon
HRX350C- HR40 40 450 Co., Ltd. 075S Mitsubishi Rayon HRX350C- HR40
40 450 Co., Ltd. 110S *Tensile strength and tensile elastic modulus
are values measured in accordance with "Carbon fiber testing
method" of JIS R7601:1986.
[0049] FIG. 2 is an expansion plan (sheet block diagram) of the
prepreg sheet forming the shaft 3. The shaft 3 includes multiple
sheets, and in the embodiment shown in FIG. 2, the shaft 3 includes
eleven sheets of a1 to a11. The expansion plan shown in FIG. 2
shows the sheets forming the shaft, sequentially from the inner
side of a radial direction of the shaft. In the expansion plan,
winding is conducted sequentially from a sheet located on the upper
side. Further, in the expansion plan shown in FIG. 2, the
right-left direction in the drawing coincides with the axial
direction of the shaft, the right side in the drawing is the tip
end 3a side of the shaft 3, and the left side in the drawing is the
butt end 3b side of the shaft 3.
[0050] It should be noted that, in the present specification, a
term "layer" and a term "sheet" are used. The "sheet" is a
designation for those prior to being wound, and the "layer" is a
designation for the sheets after being wound. The "layer" is formed
by winding the "sheet." Furthermore, in the present specification,
the same reference character is used for a layer and a sheet. For
example, a layer formed by winding the sheet a1 is described as a
layer a1.
[0051] Furthermore, in the present specification, regarding the
angle of a fiber with respect to the axial direction of the shaft,
an angle Af and an absolute angle .theta.a are used. The angle Af
is an angle that is associated with a plus or a minus, and the
absolute angle .theta.a is an absolute value of the angle Af. The
absolute angle .theta.a is an absolute value of an angle between
the axial direction of the shaft and a fiber direction. For
example, "the absolute angle .theta.a being equal to or smaller
than 10.degree." means "the angle Af being not smaller than
-10.degree. but not larger than +10.degree.".
[0052] The expansion plan shown in FIG. 2 not only shows a winding
sequence of each of the sheets, but also shows a position of each
of the sheets in the axial direction of the shaft. For example, the
end of the sheet a1 is located at the tip end 3a, and the ends of
the sheet a4 and the sheet a5 are located at the butt end 3b.
[0053] The shaft 3 includes straight layers, bias layers, and a
hoop layer. The expansion plan shown in FIG. 2 describes an
orientation angle of a fiber included in the prepreg sheet; and a
sheet having a description of "0.degree." forms a straight layer. A
sheet for the straight layer is also referred to as a straight
sheet in the present specification. In addition, a sheet for the
bias layer is also referred to as a bias sheet in the present
specification.
[0054] The straight layer is a layer whose fiber orientation is
substantially 0.degree. with respect to a longitudinal direction of
the shaft (axial direction of the shaft). However, there are cases
where the direction of the fiber is not perfectly 0.degree. with
respect to the axial direction of the shaft, due to errors at the
time of winding. Ordinarily, in the straight layer, the absolute
angle .theta.a is equal to or smaller than 10.degree..
[0055] In the embodiment shown in FIG. 2, the straight sheets are
the sheet a1, the sheet a4, the sheet a5, the sheet a6, the sheet
a7, the sheet a9, the sheet a10, and the sheet a11. The straight
layer is highly correlated with flexural rigidity and flexural
strength of the shaft.
[0056] The bias layer is a layer whose fiber orientation is slanted
with respect to the longitudinal direction of the shaft. The bias
layer is highly correlated with twist rigidity and twist strength
of the shaft. The bias layer is preferably formed from a pair of
two sheets whose fiber orientations are slanted in directions
opposite to each other. From a standpoint of twist rigidity, the
absolute angle .theta.a of the bias layer is preferably equal to or
larger than 15.degree., more preferably equal to or larger than
25.degree., and further preferably equal to or larger than
40.degree.. On the other hand, from the standpoint of twist
rigidity and twist strength, the absolute angle .theta.a of the
bias layer is preferably equal to or smaller than 60.degree., and
more preferably equal to or smaller than 50.degree..
[0057] In the embodiment shown in FIG. 2, the bias sheets are the
sheet a2 and the sheet a3. In FIG. 2, the angle Af is described for
all of the sheets. Plus (+) and minus (-) of the angles Af indicate
that fibers of the bias sheets are slanted in directions opposite
to each other. It should be noted that, in the embodiment shown in
FIG. 2, although the angle Af of the sheet a2 is -45.degree. and
the angle Af of the sheet a3 is +45.degree., contrary to that, the
angle Af of the sheet a2 may be +45.degree. and the angle Af of the
sheet a3 may be -45.degree..
[0058] In the embodiment shown in FIG. 2, the sheet forming the
hoop layer is the sheet a8. The absolute angle .theta.a of the hoop
layer is preferably substantially 90.degree. with respect to the
axial direction of the shaft. However, there are cases where the
direction of the fiber is not perfectly 90.degree. with respect to
the axial direction of the shaft, due to errors at the time of
winding. Ordinarily, in the hoop layer, the absolute angle .theta.a
is not smaller than 80.degree. but not larger than 90.degree..
[0059] The hoop layer contributes to enhancing crush rigidity and
crush strength of the shaft. The crush rigidity is rigidity against
crushing force toward the inner side of the radial direction of the
shaft. The crush strength is strength against crushing force toward
the inner side of the radial direction of the shaft. The crush
strength is also related to flexural strength. Furthermore, crush
deformation may occur associated with flexural deformation. This
association is particularly large for a thin lightweight shaft. By
improving the crush strength, flexural strength can be
improved.
[0060] Although not diagrammatically represented, the prepreg sheet
before it is being used is sandwiched between cover sheets.
Ordinarily, a cover sheet consists of a release paper and a resin
film, and the release paper is pasted on one surface of the prepreg
sheet, and the resin film is pasted on the other surface. In the
following description, the surface on which the release paper is
pasted is also referred to as "release paper side surface" and the
surface on which the resin film is pasted is also referred to as
"film side surface."
[0061] The expansion plans in the present specification are
diagrams in which the film side surface is on the front side. In
other words, in the expansion plans in the present specification,
the front side in the drawing is the film side surface, and the
reverse side in the drawing is the release paper side surface. In
the expansion plan shown in FIG. 2, the fiber direction of the
sheet a2 and the fiber direction of the sheet a3 are identical,
whereas when being attached as described later, the sheet a3 will
be turned over. As a result, the fiber direction of the sheet a2
and the fiber direction of the sheet a3 become directions opposite
to each other, and thereby, in a state after the winding, the fiber
direction of the sheet a2 and the fiber direction of the sheet a3
will be directions opposite to each other. This point is taken into
consideration, and in FIG. 2, the fiber direction of the sheet a2
is denoted as "-45.degree." and the fiber direction of the sheet a3
is denoted as "+45.degree.."
[0062] In order to wind the above described prepreg sheet, firstly,
the resin film is peeled. By peeling the resin film, the film side
surface becomes exposed. This exposed surface has tackiness
(adhesiveness) originating from the matrix resin. Since the matrix
resin of the prepreg at the time of the winding is in a semi-cured
state, the matrix resin expresses adhesiveness. Next, a margin part
(wind-start margin part) on the exposed surface of the film side is
attached to a to-be-wound object. Attaching to the wind-start
margin part can be smoothly conducted due to the adhesiveness of
the matrix resin. The to-be-wound object is a mandrel, or a wound
object obtained by winding another prepreg sheet on a mandrel.
[0063] Next, the release paper of the prepreg sheet is peeled.
Then, the to-be-wound object is rotated to wind the prepreg sheet
on the to-be-wound object. In the manner described above, first,
the resin film is peeled; next, the wind-start margin part is
attached to the to-be-wound object, and then, the release paper is
peeled. With such a procedure, occurrences of wrinkling of the
prepreg sheet and inferior winding can be prevented. The release
paper has high flexural rigidity when compared to the resin film,
and a sheet having such release paper attached thereto is supported
by the release paper and is unlikely to wrinkle.
[0064] In the embodiment shown in FIG. 2, a merged sheet formed by
attaching two or more sheets together is employed. For the
embodiment shown in FIG. 2, two merged sheets shown in FIGS. 3 and
4 are employed. FIG. 3 shows a first merged sheet a23 formed by
attaching the sheet a2 and the sheet a3 together. In addition, FIG.
4 shows a second merged sheet a89 formed by attaching the sheet a8
and the sheet a9 together.
[0065] The procedure for manufacturing the first merged sheet a23
will be described below. First, the bias sheet a3 is turned over,
and the turned over bias sheet a3 is attached to the bias sheet a2.
At that time, as shown in FIG. 3, a butt end and a tip end of the
bias sheet a3 are each attached to the bias sheet a2 so as to be
misaligned from a long side of the bias sheet a2.
[0066] As a result, the sheet a2 and the sheet a3 of the merged
sheet a23 are misaligned from each other by about half a wind in
the shaft after the winding.
[0067] As shown in FIG. 4, in the second merged sheet a89, the
upper end of the sheet a8 matches the upper end of the sheet a9.
Additionally, in the sheet a89, the entirety of the sheet a8 is
pasted on the sheet a9 in a state where a butt side end margin of
the sheet a8 is misaligned from a butt side end margin of the sheet
a9. As a result, inferior winding of the sheet a8 in the winding
step is prevented.
[0068] As described above, in the present specification, although
the sheets and layers are classified by their fiber's orientation
angle in the prepreg, the sheets and layers can be further
classified by their length in the axial direction of the shaft.
[0069] In the present specification, a layer arranged over the
whole axial direction of the shaft is referred to as a full length
layer, and a sheet arranged over the whole axial direction of the
shaft is referred to as a full length sheet. On the other hand, in
the present specification, a layer partially arranged in the axial
direction of the shaft is referred to as a partial layer, and a
sheet partially arranged in the axial direction of the shaft is
referred to as a partial sheet.
[0070] In the present specification, a straight layer that is a
full length layer is referred to as a full length straight layer.
In the embodiment shown in FIG. 2, the sheet a6 and the sheet a9
form the full length straight layers after the winding.
[0071] In addition, in the present specification, a straight layer
that is a partial layer is referred to as a partial straight layer.
In the embodiment shown in FIG. 2, the sheet a1, the sheet a4, the
sheet a5, the sheet a7, the sheet a10, and the sheet a11 form the
partial straight layers after the winding.
[0072] After the winding, the sheet a7, which is a sheet included
in the partial layers, form a middle partial layer located in the
middle of the whole axial direction of the shaft. Thus, a front end
of the middle partial layer is separated from the tip end 3a, and a
back end of the middle partial layer is separated from the butt end
3b. Preferably, the middle partial layer is arranged at a position
including a center position Sc of the axial direction of the shaft.
Furthermore, preferably, the middle partial layer is arranged at a
position including a B point (a point located 525 mm away from the
tip end) defined by a method for measuring three point flexural
strength (a measuring method for SG-type three point flexural
strength testing). The middle partial layer can selectively
reinforce a portion that has large deformation, and can also
contribute to weight reduction of the shaft.
[0073] In the present specification, a term "butt partial layer" is
used. The butt partial layer is one mode of the partial layer, and
is a partial layer that is located on the butt end 3b side. Shown
in FIG. 2 with a reference character of "A1" is a point located on
the most butt side on a side of the butt partial layer in the tip
side. Preferably, the point A1 is located closer to the butt side
than the center position Sc of the axial direction of the shaft.
Shown in FIG. 2 with a reference character of "B1" is a middle
point of a side of the butt partial layer in the tip side.
Preferably, the point B1 is located closer to the butt side than
the center position Sc of the axial direction of the shaft. The
butt partial layer includes a butt straight layer, a butt hoop
layer, and a butt bias layer.
[0074] In addition, in the present specification, a term "butt
straight layer" is used. The butt straight layer is one mode of the
partial straight layer, and is a partial straight layer located on
the butt end 3b side. Preferably, the entirety of the butt straight
layer is located closer to the butt side than the center position
Sc of the axial direction of the shaft. The back end of the butt
straight layer may or may not be located at the butt end 3b of the
shaft. From a standpoint of bringing the position of the center of
gravity of the club close to the butt end 3b, preferably, an
arrangement range of the butt straight layer includes a position P1
that is separated from the butt end 3b of the shaft by 100 mm. From
a standpoint of bringing the position of the center of gravity of
the club close to the butt end 3b, more preferably, the back end of
the butt straight layer is located at the butt end 3b of the shaft.
In the embodiment shown in FIG. 2, the butt straight layer is the
sheet a4 and the sheet a5.
[0075] The shaft 3 is manufactured through a sheet winding process
using the prepreg sheet shown in FIG. 2. In the following, a
general outline of the steps for manufacturing the shaft 3 will be
described.
[0076] [General Outline of Shaft Manufacturing Steps]
[0077] (1) Cutting Step
[0078] In a cutting step, the prepreg sheet is cut into
predetermined shapes, and each of the sheets shown in FIG. 2 is cut
out.
[0079] (2) Attaching Step
[0080] In an attaching step, multiple sheets are attached together
to manufacture the merged sheet a23 and the merged sheet a89
described above. For the attaching, applying of heat or pressing
can be used; however, from a standpoint of reducing misalignments
between sheets forming a merged sheet in a later described winding
step and improving accuracy of the winding, the applying of heat
and the pressing are preferably used in combination. Although
heating temperature and pressing pressure can be selected as
appropriate from a standpoint of enhancing the adhesive strength
among the sheets, the heating temperature is ordinarily within a
range from 30 to 60.degree. C., and the pressing pressure is
ordinarily within a range from 300 to 600 g/cm.sup.2. Similarly,
although heating time and pressing time can also be selected as
appropriate from a standpoint of enhancing the adhesive strength
among the sheets, the heating time is ordinarily within a range
from 20 to 300 seconds, and the pressing time is ordinarily within
a range from 20 to 300 seconds.
[0081] (3) Winding Step
[0082] In the winding step, a mandrel is used. A representative
mandrel is made from metal, and a mold releasing agent is applied
on a circumferential surface of the mandrel. Additionally, a resin
(tacking resin) having adhesiveness is applied over the mold
releasing agent. The cut sheets are wound on the mandrel which has
the resin applied thereon. As a result of the tacking resin, an end
part of the sheet can be attached easily to the mandrel. A sheet
obtained by attaching multiple sheets together is wound in a state
of a merged sheet.
[0083] With this winding step, a wound body can be obtained. The
wound body is obtained by winding a prepreg sheet on the outer side
of the mandrel. The winding is conducted, for example, by rolling a
to-be-wound object on a flat surface.
[0084] (4) Tape Wrapping Step
[0085] In a tape wrapping step, a tape referred to as a wrapping
tape is wound on an outer circumferential surface of the wound
body. The wrapping tape is wound on the outer circumferential
surface of the wound body while being kept in tension. With the
wrapping tape, pressure is applied to the wound body and void in
the wound body is reduced.
[0086] (5) Curing Step
[0087] In a curing step, the wound body which has been wrapped with
the tape is heated at a predetermined temperature. As a result of
the heating, the matrix resin in the prepreg sheet is cured. In the
curing process, the matrix resin temporarily fluidizes, and through
this fluidization, air within or between the sheets is discharged.
The discharging of air is enhanced by the pressure (fastening
force) provided by the wrapping tape. With the curing step, a cured
lamination body is obtained.
[0088] (6) Mandrel Draw-Out Step and Wrapping Tape Removal Step
[0089] After the curing step, a mandrel draw-out step and a
wrapping tape removal step are conducted. Although there is no
particular limitation in the sequence of the two steps in the
present invention, from a standpoint of improving efficiency of the
wrapping tape removal, the wrapping tape removal step is preferably
conducted after the mandrel draw-out step.
[0090] (7) Both-Ends Cutting Step
[0091] In a both-ends cutting step, both ends of the cured
lamination body obtained through each of the steps of (1) to (6)
described above are cut. As a result of the cutting, the end
surface of the tip end 3a and the end surface of the butt end 3b of
the shaft become smooth.
[0092] (8) Polishing Step
[0093] In a polishing step, the surface of the cured lamination
body whose both ends are cut is polished. Helical concavities and
convexities remain on the surface of the cured lamination body as
traces of the wrapping tape used in step (4) described above. As a
result of the polishing, the helical concavities and convexities
which are traces of the wrapping tape disappear, and the surface of
the cured lamination body becomes smooth.
[0094] (9) Painting Step
[0095] A prescribed paint is applied on the cured lamination body
after the polishing step.
[0096] With the above described steps, the shaft 3 can be
manufactured. The golf club 1 can be obtained by fixing the tip end
3a of the manufactured shaft 3 in the shaft hole 5 of the hosel 6
of the golf club head 2, and fixing the butt end 3b of the shaft 3
in the grip hole 7 of the grip 4.
[0097] One feature of the present invention is that, in the golf
club 1 described above, when the distance from the front end 3a of
the shaft 3 to the center of gravity of the shaft is represented as
L.sub.G and when the full length of the shaft is represented as
L.sub.S, for example, 0.5.ltoreq.L.sub.G/L.sub.S.ltoreq.0.67 is
satisfied and the center of gravity G of the shaft 3 is brought
close to the hand side.
[0098] Reducing club weight is effective in making the club easy to
swing. However, the weight of the head which is one element forming
the club is a factor that influences an increase in ball speed.
Therefore, in the present invention, an approach of increasing the
ball speed without reducing the head weight is adopted. By placing
the position of the center of gravity of the shaft on the grip
side, the inertia moment of the club is reduced to make the club
easy to swing.
[0099] Means for adjusting the position of the center of gravity of
the shaft 3 includes, for example, the following (A) to (H). In the
present invention, it is possible to bring the position of the
center of gravity of the shaft 3 close to the hand side by
employing one or more of these means as appropriate.
(A) Increasing or decreasing the number of windings of the butt
partial layer (B) Increasing or decreasing the thickness of the
butt partial layer (C) Increasing or decreasing a length L1
(described later) of the butt partial layer (D) Increasing or
decreasing a length L2 (described later) of the butt partial layer
(E) Increasing or decreasing the number of windings of the tip
partial layer (F) Increasing or decreasing the thickness of the tip
partial layer (G) Increasing or decreasing a shaft-direction length
of the tip partial layer (H) Increasing or decreasing a taper rate
of the shaft
[0100] <Weight Ratio of Butt Partial Layer>
[0101] From a standpoint of placing the position of the center of
gravity of the shaft on the grip side, the weight of the butt
partial layer with respect to the shaft weight is preferably not
smaller than 5 wt %, and more preferably not smaller than 10 wt %.
On the other hand, from a standpoint of reducing a stiff feeling,
the weight of the butt partial layer with respect to the shaft
weight is preferably not larger than 50 wt %, and more preferably
not larger than 45 wt %. In the embodiment shown in FIG. 2, a total
weight of the sheet a4 and the sheet a5 is the weight of the butt
partial layer.
[0102] <Weight Ratio of Butt Partial Layer in Specific Butt
Range>
[0103] Indicated as "P2" in FIG. 1 is a point separated from the
butt end 3b by 250 mm. A range from point P2 to the butt end 3b is
defined as a "specific butt range." When the weight of the butt
partial layer existing in the specific butt range is represented as
"Wa," and when the weight of the shaft in the specific butt range
is represented as "Wb," from a standpoint of placing the position
of the center of gravity of the shaft on the grip side, the ratio
(Wa/Wb) is preferably not lower than 0.4, more preferably not lower
than 0.42, and further preferably not lower than 0.44. On the other
hand, from a standpoint of reducing a stiff feeling, the ratio
(Wa/Wb) is preferably not higher than 0.7, more preferably not
higher than 0.65, and further preferably not higher than 0.6
[0104] <Fiber Elastic Modulus of Butt Partial Layer>
[0105] From a standpoint of ensuring strength of the butt partial
layer, the fiber elastic modulus of the butt partial layer is
preferably not lower than 5 t/mm.sup.2, and more preferably not
lower than 7 t/mm.sup.2. When the center of gravity of the club is
close to the butt end 3b, centrifugal force that acts upon the
center of gravity of the club easily decreases. In other words,
when the center-of-gravity position of the shaft is placed on the
grip side, the centrifugal force that acts upon the center of
gravity of the club easily decreases. In such a case, it becomes
difficult to sense the bending of the shaft, and a stiff feeling is
easily generated. From a standpoint of reducing a stiff feeling,
the fiber elastic modulus of the butt partial layer is preferably
not higher than 20 t/mm.sup.2, more preferably not higher than 15
t/mm.sup.2, and further preferably not higher than 10
t/mm.sup.2
[0106] <Resin Content of Butt Partial Layer>
[0107] From a standpoint of placing the center-of-gravity position
of the shaft on the grip side and reducing a stiff feeling, the
resin content of the butt partial layer is preferably not lower
than 20 mass %, and more preferably not lower than 25 mass %. On
the other hand, from a standpoint of ensuring strength of the butt
partial layer, the resin content of the butt partial layer is
preferably not higher than 50 mass %, and more preferably not
higher than 45 mass %.
[0108] <Weight of Butt Straight Layer>
[0109] From a standpoint of placing the position of the center of
gravity of the shaft on the grip side, the weight of the butt
straight layer is preferably not smaller than 2 g, and more
preferably not smaller than 4 g. On the other hand, from a
standpoint of reducing a stiff feeling, the weight of the butt
straight layer is preferably not larger than 30 g, more preferably
not larger than 20 g, and further preferably not larger than 10
g.
[0110] <Weight Ratio of Butt Straight Layer>
[0111] From a standpoint of placing the position of the center of
gravity of the shaft on the grip side, the weight of the butt
straight layer with respect to the shaft weight Ws is preferably
not smaller than 5 mass %, and more preferably not smaller than 10
mass %. On the other hand, from a standpoint of reducing a stiff
feeling, the weight of the butt straight layer with respect to the
shaft weight is preferably not larger than 50 mass %, and more
preferably not larger than 45 mass %. In the embodiment shown in
FIG. 3, the total weight of the sheet a4 and the sheet a5 is the
weight of the butt straight layer.
[0112] <Fiber Elastic Modulus of Butt Straight Layer>
[0113] From a standpoint of ensuring strength of the butt part, the
fiber elastic modulus of the butt straight layer is preferably not
lower than 5 t/mm.sup.2, and more preferably not lower than 7
t/mm.sup.2. On the other hand, from a standpoint of reducing a
stiff feeling, the fiber elastic modulus of the butt straight layer
is preferably not higher than 20 t/mm.sup.2, more preferably not
higher than 15 t/mm.sup.2, and further preferably not higher than
10 t/mm.sup.2.
[0114] <Resin Content of Butt Straight Layer>
[0115] From a standpoint of placing the position of the center of
gravity of the shaft on the grip side, and reducing a stiff
feeling, the resin content of the butt straight layer is preferably
not lower than 20 mass %, and more preferably not lower than 25
mass %. On the other hand, from a standpoint of ensuring strength
of the butt part, the resin content of the butt straight layer is
preferably not higher than 50 mass %, and more preferably not
higher than 45 mass %.
[0116] <Maximum Shaft Direction Length L1 of Butt Partial
Layer>
[0117] Shown as "L1" in FIG. 2 is the maximum shaft direction
length of the butt partial layer. The maximum length L1 is
determined in each butt partial sheet. In the embodiment shown in
FIG. 2, a length L1 of the sheet a4 is different from a length L1
of the sheet a5.
[0118] From a standpoint of ensuring weight of the butt partial
layer, the length L1 is preferably not smaller than 100 mm, more
preferably not smaller than 125 mm, and further preferably not
smaller than 150 mm. On the other hand, from a standpoint of
placing the position of the center of gravity of the shaft on the
grip side, the length L1 is preferably not larger than 700 mm, more
preferably not larger than 650 mm, and further preferably not
larger than 600 mm.
[0119] <Minimum Shaft Direction Length L2 of Butt Partial
Layer>
[0120] Shown as "L2" in FIG. 2 is the minimum shaft direction
length of the butt partial layer. The minimum length L2 is
determined in each butt partial sheet. In the embodiment shown in
FIG. 2, a length L2 of the sheet a4 is different from a length L2
of the sheet a5.
[0121] From a standpoint of ensuring weight of the butt partial
layer, the length L2 is preferably not smaller than 50 mm, more
preferably not smaller than 75 mm, and further preferably not
smaller than 100 mm. On the other hand, from a standpoint of
placing the position of the center of gravity of the shaft on the
grip side, the length L2 is preferably not larger than 650 mm, more
preferably not larger than 600 mm, and further preferably not
larger than 550 mm.
EXAMPLES
[0122] Next, the golf club of the present invention will be
described based on Examples; however, the present invention is not
limited only to those Examples.
[0123] Golf clubs according to Examples 1 to 21 and Comparative
Examples 1 to 15 were manufactured in accordance with a hitherto
known method, and their performances and characteristics were
evaluated. A substantially identical shaped head was used for all
the golf clubs, and the volume of the head was 460 cc, and the
material of the head was a titanium alloy. Head weights, grip
weights, shaft weights, shaft lengths etc., were adjusted so as to
obtain desired specifications.
[0124] Shafts for the Examples and Comparative Examples were
manufactured based on the expansion plan shown in FIG. 2. The used
manufacturing method was similar to that used for the shaft 3
described above, and the shafts were manufactured in accordance
with the steps of (1) to (9). For each of the sheets a1 to a11, the
number of windings, the thickness of the prepreg, the fiber content
of the prepreg, and the tensile elastic modulus of carbon fiber
etc., were selected as appropriate. Examples of the prepregs used
for the shafts in the Examples and Comparative Examples are shown
in Table 2. For adjusting the position of the center of gravity of
the shafts, one or more of the above described (A) to (H) were
used.
TABLE-US-00003 TABLE 2 Specification of Prepreg Sheet Carbon Fiber
Physical Property Value Reference Prepreg Sheet Fiber Resin Carbon
Fiber Tensile Elastic Tensile Character Sheet Stock Thickness
Content Content Stock Modulus Strength of Cut Sheet Manufacturer
Name Number (mm) (Mass %) (Mass %) Number (t/mm.sup.2)
(kgf/mm.sup.2) a1 Nippon Graphite Fiber E1026A-14N 0.15 63 37 XN-10
10 190 Corp. a2, a3 Toray Industries, Inc. 9255S-8 0.061 76 24 M40S
40 470 a4 Nippon Graphite Fiber E1026A-09N 0.1 63 37 XN-10 10 190
Corp. a5 Mitsubishi Rayon MR350C-125S 0.104 75 25 TR50S 24 500 Co.,
Ltd. a6, a7, a10, a11 Mitsubishi Rayon TR350C-100S 0.083 75 25
TR50S 24 500 Co., Ltd. a8 Toray Industries, Inc. 805S-3 0.0342 60
40 M30S 30 560 a9 Mitsubishi Rayon TR350C-175S 0.146 75 25 TR50S 24
500 Co., Ltd.
[0125] Specifications and evaluations of the golf clubs according
to Examples 1 to 7 and Comparative Examples 1 and 2 (the club
weights are set to 280 g) are shown in Table 3. In addition,
specifications and evaluations of the golf clubs according to
Examples 8 to 14 and Comparative Examples 3 and 4 (the club weights
are set to 306 g) are shown in Table 4. Further, specifications and
evaluations of the golf clubs according to Examples 15 to 21 and
Comparative Examples 5 and 6 (club weights are set to 338 g) are
shown in Table 5. Further, specifications and evaluations of the
golf clubs according to Comparative Examples 7 to 15 (the club
weights are set to 350 g) are shown in Table 6.
TABLE-US-00004 TABLE 3 Specifications and Evaluation Results of
Examples and Comparative Examples (Club Weight: 280 g) Change
Position of Shaft Center-of-Gravity (L.sub.G/Ls) Change Head
Weight/Club Weight Comp. Ex. Ex. Ex. Ex. Comp. Ex. Ex. Ex. Ex. 1 1
2 3 4 Ex. 2 5 6 7 Club Weight [g] 280 280 280 280 280 280 280 280
280 "Head Weight Ratio (Head Weight/ 0.360 0.368 0.380 0.395 0.410
0.360 0.368 0.395 0.410 Club Weight)" .times. "Position of Shaft
Center-of-Gravity (L.sub.G/Ls)" Head Weight [g] 192.0 192.0 192.0
192.0 192.0 182.0 186.0 199.7 207.3 Head Weight/Club Weight 0.69
0.69 0.69 0.69 0.69 0.65 0.66 0.71 0.74 Club Length [inch] 45.5
45.5 45.5 45.5 45.5 45.5 45.5 45.5 45.5 Position of Shaft 0.525
0.537 0.554 0.576 0.598 0.554 0.554 0.554 0.554 Center-of-Gravity
(L.sub.G/Ls) Shaft Length [mm] 1150 1150 1150 1150 1150 1150 1150
1150 1150 Grip Weight [g] 37.5 37.5 37.5 37.5 37.5 37.5 37.5 37.5
37.5 Head Speed [m/s] 39.5 39.8 40.0 40.2 40.4 40.5 40.4 39.5 39.1
Kinetic Energy [J] 149.8 152.1 153.6 155.1 156.7 149.2 151.8 155.8
158.4 Ball Flight Distance [yards] 198 202 204 206 208 198 202 207
211 Shaft Durability A A A A B A A A B
TABLE-US-00005 TABLE 4 Specifications and Evaluation Results of
Examples and Comparative Examples (Club Weight: 306 g) Change
Position of Shaft Center-of-Gravity (L.sub.G/Ls) Change Head
Weight/Club Weight Comp. Ex. Ex. Ex. Ex. Comp. Ex. Ex. Ex. Ex. 3 8
9 10 11 Ex. 4 12 13 14 Club Weight [g] 306 306 306 306 306 306 306
306 306 "Head Weight Ratio (Head Weight/ 0.360 0.368 0.380 0.395
0.410 0.360 0.368 0.395 0.410 Club Weight)" .times. "Position of
Shaft Center-of-Gravity (L.sub.G/Ls)" Head Weight [g] 218.0 218.0
218.0 218.0 218.0 206.5 211.1 226.6 235.2 Head Weight/Club Weight
0.712 0.712 0.712 0.712 0.712 0.675 0.690 0.740 0.769 Club Length
[inch] 40.5 40.5 40.5 40.5 40.5 40.5 40.5 40.5 40.5 Position of
Shaft 0.505 0.517 0.533 0.554 0.576 0.533 0.533 0.533 0.533
Center-of-Gravity (L.sub.G/Ls) Shaft Length [mm] 1025 1025 1025
1025 1025 1025 1025 1025 1025 Grip Weight [g] 37.5 37.5 37.5 37.5
37.5 37.5 37.5 37.5 37.5 Head Speed [m/s] 37.4 37.6 37.6 37.7 37.8
38.3 38.1 37.3 36.8 Kinetic Energy [J] 152.5 153.9 154.5 155.2
155.9 151.5 153.2 157.2 159.6 Ball Flight Distance [yards] 177 181
181 182 183 176 181 184 186 Shaft Durability A A A A B A A A B
TABLE-US-00006 TABLE 5 Specifications and Evaluation Results of
Comparative Examples (Club Weight: 338 g) Change Position of Shaft
Center-of-Gravity (L.sub.G/Ls) Change Head Weight/Club Weight Comp.
Ex. Ex. Ex. Ex. Comp. Ex. Ex. Ex. Ex. 5 15 16 17 18 Ex. 6 19 20 21
Club Weight [g] 338 338 338 338 338 338 338 338 338 "Head Weight
Ratio (Head Weight/ 0.360 0.368 0.380 0.395 0.410 0.360 0.368 0.395
0.410 Club Weight)" .times. "Position of Shaft Center-of-Gravity
(L.sub.G/Ls)" Head Weight [g] 240.0 240.0 240.0 240.0 240.0 227.4
232.4 249.5 258.9 Head Weight/Club Weight 0.710 0.710 0.710 0.710
0.710 0.673 0.688 0.738 0.766 Club Length [inch] 39.5 39.5 39.5
39.5 39.5 39.5 39.5 39.5 39.5 Position of Shaft 0.507 0.518 0.535
0.556 0.577 0.535 0.535 0.535 0.535 Center-of-Gravity (L.sub.G/Ls)
Shaft Length [mm] 995 995 995 995 995 995 995 995 995 Grip Weight
[g] 37.5 37.5 37.5 37.5 37.5 37.5 37.5 37.5 37.5 Head Speed [m/s]
35.2 35.5 35.6 35.7 35.8 36.1 35.9 35.3 34.9 Kinetic Energy [J]
148.7 151.2 152.1 152.9 153.8 148.4 150.1 155.1 157.4 Ball Flight
Distance [yards] 166 171 172 173 174 167 170 175 178 Shaft
Durability A A A A B A A A B
TABLE-US-00007 TABLE 6 Specifications and Evaluation Results of
Comparative Examples (Club Weight: 350 g) Change Position of Shaft
Center-of-Gravity (L.sub.G/Ls) Change Head Weight/Club Weight Comp.
Comp. Comp. Comp. Comp. Comp. Comp. Comp. Comp. Ex. 7 Ex. 8 Ex. 9
Ex. 10 Ex. 11 Ex. 12 Ex. 13 Ex. 14 Ex. 15 Club Weight [g] 350 350
350 350 350 350 350 350 350 "Head Weight Ratio (Head Weight/ 0.360
0.368 0.380 0.395 0.410 0.360 0.368 0.395 0.410 Club Weight)"
.times. "Position of Shaft Center-of-Gravity (L.sub.G/Ls)" Head
Weight [g] 240.0 240.0 240.0 240.0 240.0 227.4 232.4 249.5 258.9
Head Weight/Club Weight 0.69 0.69 0.69 0.69 0.69 0.65 0.66 0.71
0.74 Club Length [inch] 39.5 39.5 39.5 39.5 39.5 39.5 39.5 39.5
39.5 Position of Shaft 0.525 0.537 0.554 0.576 0.598 0.554 0.554
0.554 0.554 Center-of-Gravity (L.sub.G/Ls) Shaft Length [mm] 995
995 995 995 995 995 995 995 995 Grip Weight [g] 37.5 37.5 37.5 37.5
37.5 37.5 37.5 37.5 37.5 Head Speed [m/s] 34.9 35.0 35.0 35.1 35.2
35.5 35.3 34.5 34.1 Kinetic Energy [J] 146.3 146.7 147.3 148.0
148.7 143.4 145.0 148.5 150.6 Ball Flight Distance [yards] 165 166
167 168 169 162 164 168 169 Shaft Durability A A A B B A A A B
[0126] [Evaluation Method]
[0127] <Head Speed (m/s)>
[0128] Five testers having handicaps of 10 to 20 were asked to each
test-hit 10 balls, and an average value of the obtained 50 head
speeds was used.
[0129] <Kinetic Energy (J)>
[0130] Kinetic energy was calculated using E=(mh.times.v.sup.2)/2.
Here, mh is head weight and v is head speed.
[0131] <Ball Flight Distance (yards)>
[0132] Five testers having handicaps of 10 to 20 were asked to each
test-hit 10 balls, and an average value (an average value of flight
distances of 8.times.5=40 shots) of flight distances to drop points
of balls for the best 8 shots excluding miss-shots was used.
[0133] <Shaft Durability>
[0134] The golf clubs were mounted on a swing robot manufactured by
Miyamae K.K., and golf balls were repeatedly hit at a head speed of
52 m/s. As the golf ball, "DDH Tour Special" manufactured by SRI
Sports Ltd., was used. Balls were hit at a position 20 mm away from
a face center to a heel side, and a damage status of the shaft was
examined every time 500 shots were hit. When there was no damage
after 10000 shots, it was evaluated as "A"; and when there was
damage before reaching 10000 shots, it was evaluated as "B."
[0135] It can be understood from the results shown in Tables 3 to 6
that the golf clubs according to the Examples can extend flight
distance of the ball by increasing head speed. In contrast, for
example, when the club weight is large as in the case with
Comparative Examples 7 to 15, flight distance cannot be
extended.
[0136] [Other Modifications]
[0137] It should be understood that the embodiments disclosed
herein are merely illustrative and not restrictive in all aspects.
The scope of the present invention is defined by the scope of the
claims rather than by the meaning described above, and is intended
to include meaning equivalent to the scope of the claims and all
modifications within the scope.
[0138] For example, in the above described embodiment, although a
shaft having the expansion plan shown in FIG. 2 is adopted as the
shaft of the golf club, the present invention is not limited
thereto, and, for example, a shaft having an expansion plan shown
in FIG. 5 may also be used. The shaft having the expansion plan
shown in FIG. 5 includes twelve sheets of b1 to b12. Similar to
FIG. 2, the expansion plan shown in FIG. 5 shows the sheets forming
the shaft, sequentially from the inner side of the radial direction
of the shaft; and winding is conducted sequentially from a sheet
located on the upper side in the expansion plan. Further, in the
expansion plan shown in FIG. 5, the right-left direction in the
drawing coincides with the axial direction of the shaft, the right
side in the drawing is the tip end 3a side of the shaft 3, and the
left side in the drawing is the butt end 3b side of the shaft
3.
[0139] In a modification shown in FIG. 5, the sheet b1, the sheet
b5, the sheet b6, the sheet b7, the sheet b8, the sheet b10, the
sheet b11, and the sheet b12 are sheets forming the straight
layers; the sheet b2 and the sheet b3 are sheets forming the bias
layers; and the sheet b4 and the sheet b9 are sheets forming the
hoop layers. As the sheets b1 to b12, for example, the following
prepregs shown in Table 1 can be used.
[0140] Sheet b1: TR350C-125S
[0141] Sheets b2, b3: HRX350C-075S
[0142] Sheet b4: 805S-3
[0143] Sheets b5, b6: E1026A-09N
[0144] Sheets b7, b8: TR350C-100S
[0145] Sheet b9: 805S-3
[0146] Sheet b10: MR350C-100S
[0147] Sheets b11, b12: TR350C-100S
[0148] In the modification shown in FIG. 5, the major difference
from that shown in FIG. 2 is arrangement of the sheet b4, which
forms the partial hoop layer, between the sheets b5 and b6, which
form the partial straight layers, and the sheets b2 and b3, which
form the bias layers.
[0149] Also in the modification shown in FIG. 5, a merged sheet
formed by attaching two or more sheets together is employed. In the
modification shown in FIG. 5, two merged sheets shown in FIGS. 6
and 7 are employed. FIG. 6 shows a first merged sheet b234 formed
by attaching the sheet b2, the sheet b3, and the sheet b4 together.
In addition, FIG. 7 shows a second merged sheet b910 formed by
attaching the sheet b9 and the sheet b10 together.
[0150] The procedure for manufacturing the first merged sheet b234
will be described below. A pre-merged sheet b34 is manufactured by
attaching two sheets (bias sheet b3 and hoop sheet b4) together.
When manufacturing the pre-merged sheet b34, the bias sheet b3 is
turned over and attached to the hoop sheet b4. In the pre-merged
sheet b34, the upper end of the sheet b4 matches the upper end of
the sheet b3. Next, the pre-merged sheet b34 and the bias sheet b2
are attached together. The pre-merged sheet b34 and the bias sheet
b2 are attached together in a state where they are misaligned from
each other by half a wind.
[0151] In the merged sheet b234, the sheet b2 and the sheet b3 are
misaligned from each other by half a wind. Thus, in the shaft after
the winding, the circumferential direction position of the sheet b2
and the circumferential direction position of the sheet b3 are
different. The angular difference here is preferably 180.degree.
(.+-.15.degree.).
[0152] As a result of using the merged sheet b234, the bias layer
b2 and the bias layer b3 are misaligned from each other in the
circumferential direction. With this misalignment, the positions of
the ends of the bias layers are spread in the circumferential
direction. As a result, it is possible to improve uniformity of the
shaft in the circumferential direction. Further, in the merged
sheet b234 in the present modification, the entirety of the hoop
sheet b4 is sandwiched between the bias sheet b2 and the bias sheet
b3. With this, it is possible to prevent inferior winding of the
hoop sheet b4 in the winding step. By using the merged sheet b234,
it is possible to improve accuracy of the winding. Here, inferior
winding means disarray of fibers, generation of wrinkles, and
deviation of fiber angle, etc.
[0153] Further, as shown in FIG. 7, in the second merged sheet
b910, the upper end of the sheet b9 matches the upper end of the
sheet b10. In addition, in the sheet b910, the entirety of the
sheet b9 is pasted on the sheet b10. As a result, inferior winding
of the sheet b9 is prevented in the winding step.
[0154] Also in the present modification, it is possible to adjust
and bring the position of the center of gravity of the shaft close
to the hand side by employing one or more of the previously
described means of (A) to (H).
REFERENCE SIGNS LIST
[0155] 1 wood-type golf club [0156] 2 head [0157] 3 shaft [0158] 3a
tip end [0159] 3b butt end [0160] 4 grip [0161] 4e grip end [0162]
5 shaft hole [0163] 6 hosel [0164] 7 grip hole [0165] G center of
gravity of shaft [0166] L.sub.G distance from the tip end of the
shaft to the center of gravity of the shaft [0167] L.sub.S shaft
full length
* * * * *